498 L. BOLK 



termination of the development of the skull. Exceptions to 

 this rule are very infrequent. 



Table 1 gives a brief resume of the above described groups 

 of my collection: 



TABLE 1 



Soon after the beginning of my investigations, the fact struck 

 me that the closing of so-called persisting sutures in skulls of 

 non-adults occurs more frequently than I had supposed. How- 

 ever, this is not the case with all cranial sutures in the same 

 degree. In some a premature concrescence is an unusual rarity, 

 but on the other hand there are some in which the concrescence 

 occurs so often, that it can scarcely be considered as an anom- 

 aly. Now in this communication, I will discuss first: those 

 sutures which I found most frequently closed, and second: 

 those in which coalescence appeared as a very exceptional 

 variety. 



PREMATURE OBLITERATION OF THE MASTO-OCCIPITAL SUTURE 



The examination of this suture produced one of the most sur- 

 prising results of my investigation. Fredericg, in his very ex- 

 tensive and valuable paper ''On the obliteration of the cranial 

 suture, "1 asserts that the coalescence of the occipital and the 

 temporal bones does not occur before the thirty-first year, it 

 being a very rare exception when it has already occurred in the 

 twenty-first or twenty-fourth year (loc. cit., p. 441). On an- 

 other page in the same work the author strongly points out the 



• Zeitschrift fur Morphologie und Anthropologie, B. 9, 1906. 



